By Dr. Geoffrey Modest
The USPSTF recently restated their prior recommendation to NOT check for asymptomatic carotid stenosis (see Ann Intern Med. 2014;161:356-362). This is based both on the potential risks of both screening and treatment, and some studies showing decreased benefit: current medical therapy may be associated with fewer strokes than when the initial studies on carotid endarterectomy were done. These older studies had found that in patients with asymptomatic carotid stenosis, carotid endarterectomy when done in a referral facility with consistently low peri-procedural morbidity/mortality, the procedure decreased the overall risk of strokes by about 50%. As a consequence of these earlier studies, a study in2011 found that more than 90% of carotid interventions were for asymptomatic carotid stenoses in the US Medicare population (vs 0% in Denmark!!). One of the concerns about medical management of internal carotid stenosis was that progression to occlusion was likely devastating. A new study in JAMA Neurology confirmed that the current medical therapies are in fact associated with much lower progression to carotid occlusion, and that occlusion itself was rarely associated with clinical stroke, further supporting the USPSTF recommendation (See doi:10.1001/jamaneurol.2015.1843).
Details:
- Retrospective review of data from 2 stoke prevention clinics in Canada from 1990 (when they began annual carotid ultrasound surveillance) until 2013, looking at ipsilateral stroke or TIA, death from ipsilateral stroke, or death from unknown cause
- 3681 patients in the database (mean age 66, 71% men, 78% hypertensive with mean BP 148/80 presumably on meds, 68% hyperlipidemic), with carotid stenosis measured by ultrasound/Doppler
Results:
- 316 (8.6%) were asymptomatic before an index occlusion that occurred during the observation period
- Of these 316 patients, 13% had prior MI, 21% diabetes, 22% smoked/ 53% had quit smoking/12% never smoked
- 80% of these occlusions occurred prior to 2002, when medical therapy was less intensive, with decreasing frequency over time (254 cases before 2002, 39 in 2002-7, and 7 after 2010)
- Only 1 patient had an ipsilateral stroke at the time ofcarotid occlusion, and 3 had ipsilateral stroke during follow-up (all before 2005)
- Of the 316 who had a carotid occlusion, 71 died over mean of 7.2 years after the occlusion, with the major known causes being MI (16%), cancer (13%), sudden death (11%), sepsis (11%), though 23% were of unknown cause
- The total carotid plaque area was significantly related inversely to event-free survival, as was age and male sex (but not the % of stenosis)
- Similar results were found for contralateral occlusion
So, a few issues:
- This observational study is consistent with others that suggest that optimal medical therapy seems to be strongly associated with decreases in carotid artery stenosis progression, and that the effect of complete occlusion is not as dire as feared (likely thanks to the rich collateral circulation in the brain).
- I think the presence of carotid stenosis, whether symptomatic or not, should trigger an aggressive medical response, since atherosclerotic disease in the carotids is a marker of atherosclerotic disease elsewhere (including the coronaries, i.e. it is a “coronary artery disease equivalent”).
- The cornerstones of this aggressive medical response should include lifestyle interventions (diet, exercise, not smoking), as well as high-potency statins, optimizing blood pressure and diabetes control, and antiplatelet drug therapy (see doi.org/10.1016/j.jacc.2014.12.045).
- There is a recently started 2-center study which will formally answer the question of medical vs surgical management: the CREST-2 trial (Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis Study) is a 4-year trial which will compare maximal medical therapy vs that plus carotid endarterectomy in one wing, and that plus carotid stent in the other, with results expected by December 2020.
- But, for now, it the data support not screening for asymptomatic carotid stenosis and that the primary treatment is aggressive lifestyle and medical management.